Electrooptical transmission



Jan. 29, 1935. H. E. IVES ELECTROOPTICAL TRANSMISSION 3 Sheets-Sheet 1Filed July 11, 1928 NR N NM R

//v|//vTOH BY HERBERT E lvss ATTORNEY Jan. 29, 1935. H.. E. IVESELECTROOPTICAL TRANSMISSION Filed July 11, 1923 5 Sheets-Sheet 2 HERBERTL. lvzs ATTORNEY Patented Jan. 29, 1935.

UNITED STATES PATENT OFFICE- ELECTROOPTICAL TRANSMISSION Herbert E.Ives, Montclair, N. "1., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationJuly 11, 1928, Serial No. 291.744

6 Claims. (01. 178-6) This invention relates to electro-optical systems,and more particularly to means for multiple channel transmission ofimages of still or -moving objects or of pictures.

An object of this invention is to provide an form of the invention,moreover, is intended for use with the type of system in which aplurality of separate transmission channels are utilized simultaneouslyto transmit the image currents, the current over each channelcorresponding to 0 the tone values of lines of elemental areas of theobject field, which lines are interspersed with other lines, the imagecurrents of which are transmitted over other channels. This'type ofsystem has the advantage that the effect of differences in transmissioncharacteristics of the various channels upon the receiving field is muchless'than would be the case if each channel were to transmit a largesection of the field as has heretofore been proposed. This effect mightbe even less objectionable if, as has also been heretofore proposed, aseparate channel were assigned to each line of the object field, butthis method is not commercially practicable because of the large numberof channels required.

In accordance with this invention, simple and reliable means areprovided for carrying out the necessary scanning processes at both thetransmitter and the receiver. In a preferred embodiment of the inventionchannel terminating means are employed which include scanning meanscomprising a spirally apertured scanning disc atboth the transmittingand the receiving stations the apertures being covered with lightdeviating means, preferably prisms, for directing light between eachline of elemental areas of 0 the field and the translating apparatusassociated with the corresponding telephone line or other transmissionchannel. The total number of apertures in the scanning disc is equallydivided among the-several channels. The scanning discs used at thetransmitting and at the receiving stations are similar.

The invention also contemplates combining the described multiple channelmethod with light amplification, effected by taking a moving picture ofthe object field and immediately developing and scanning the developedpicture, whereby a very great additional gain in effective availablelight is obtained. Such amplification is particularly useful withmultiple channel operation, 5' 5 since with ordinary flood lightingsufficient illumination for goodresults may not be obtainable, andillumination with a moving beam of light cannot readily be usedbecause'of the diniculty of preventing interference between dif= ferentlight channels. V v

A more detailed description of the invention follows and is illustratedin the accompanying drawings.

Fig. l is a schematic representation of a multiple channel televisionsystem arrangedfor directly viewing the produced image.

Fig. 2 is a front side view of a fragmentary por,- tion of the scanningdisc showing particularly the arrangement of the scanning aperturesandtheir position with reference to the scanning ,or view,- ing area ata given instant. 1 r

Fig. 3 is a rear side View of a portionjof the scanning disc showing anendof a prism asso ciated with an aperture. 25

Fig. 4 is a schematic drawing showing sections of the scanning disc,the. direction-ofthe light beam entering and leaving each of threeadjoining apertures each associated with "different channelsand thearrangement of the refracting 30 prisms in a preferred arrangement.

Fig. 5 is a section'view .of a portion of the scanning disc through anaperture and'a: side view of an associated prism of the reflecting typ ri Fig. 6 is a schematic representation of a multi-ple channel televisionsystem employing the transmitting apparatus shown in Fig. 1 andreceiving apparatus arranged for producing the image on a large multipleelement grid type receiving lamp.

Fig. 7 is a schematic representation of the transmitting apparatus of'amultiple channel television system arranged for rapidly photographing anobject on a moving film and-for translating with the aid of lightamplification the light efiects recorded on the film into electriccurrents for "transmission over a pluralityof transmission channels.

Fig. 8 is a schematic representation of the receiving apparatus of amultiple channel television system arranged forrapidly photographicallyreceiving the image on a moving picture film and for projecting with theaid of light amplification thelimag'e after quick development of thefilm on a large viewing screen.

Fig. 9 is a side View of a scanning disc showing a modified arrangementof the scanning apertures for use with a continuously movingphotographic film.

Referring to Fig. 1, the object 10 is scanned by the multiple channelscanning apparatus 30. An image of an illuminated object or field ofview is formed by means of a suitable objective lens system 11 on thescanning area of the scanning disc 31 in substantially the same manneras an image of an object to be photographed is formed upon aphotographic film. The lens system 12-13 concentrates the light raysfrom the lens 11 into an image of restricted area in the plane of thephotoelectric cell or cells. Each aperture 1a, 2b, 30, etc., of thescanning disc is equipped with a light deflecting element, such as aprism,

the function of the prisms being to divide the light and direct thebeams in a predetermined direction upon a plurality of light sensitivecells 41a, 42b, 430, etc., originating a corresponding number ofseparate electrical transmission channels. Three channels have beenshown for illustrating the invention but obviously a different numbermay be used. The angle of refraction of each of the separate prismsassociated with the apertures 1a, 2b, and 3c is such that. the lightpassing through the prisms is always directed to one of the points oforigin of the several electrical transmission channels, the lightsensitive cells 41a, 42b, and 430, respectively; and succeedingapertures of the scanning disc such as 4a, 5b, and 60, shown in Fig. 2,when they pass before the viewing field similarly direct the light fromthe object in different directions to the corresponding light sensitivecells 41a, 42b, and 43c, respectively. Succeeding apertures as thescanning disc rotates repeat the process. In the case shown every thirdaperture directs its light rays to the same light sensitive cell ortransmission channel. The condensing or projection lens system 12-13 isarranged to form an image of the objective lens 11 on the lightsensitive cells while the prisms 0n the scanning disc determine whichcell or channel is to be activated by a given scanhing light beam. Theproper relationship between the size and focal length of the objectivelens 11 and the projection lens system 12-13 and the angles of theprisms should be observed in b'rder that the spread of thelight channelto each of the light sensitive cells 41a, 42b, and 43:2 for the severalrespective channels is so limited that the light channels do not overlapand cause interfe'rence between the different channels. In the preferredarrangement elemental areas of juxtapositioned lines of the object whoseimage is transmitted are simultaneously scanned and elemental areas ofeach series of juxtapositioned li'nes are simultaneously transmitted bya plurahty of transmission channels as is obvious from thearrangementshown in the drawings. Other positioning of the lines ofelemental areas in scanning may be arranged. The scanning disc 31 isdriven in synchronism, by any suitable means such as the motor 32, witha similar scanning disc at the receiving station. The photoelectriccurrent generated in the light sensitive cells originating eachtransmission channel is amplified for, transmission by suitableamplifiers 51, 52, and 53. l g

, The receiving apparatus is connected with the transmitting apparatusSOby means of suitable transmission channels 61 62, and 63, such as wireor radio channels, though only the former is shown in the drawings. Thereceived photo- ,over the transmission channel with which each is"connected. The lens system 9392 images the light sources 81a, 82b, and830 in the eye of the observer through the aperture in the observerpositioning plate 91. A scanning disc 31 having apertures 1a; 2b; 30,etc. carrying prisms associated with each aperture similar to that atthe transmittingstation directs the scanning light beams into the eye ofthe observer so as to scan the produced image in synchronism with thescanning operation at the transmitting station. The receiving sources oflight may be of any suitable type producing a small size intense lightwhich varies in accordance with the exciting current. A glow dischargelamp suitable for this is shown in the patent to Frank Gray, No.1,830,163, dated November 3, 1931.

The arrangement of the scanning disc apertures in relation to theviewing area at a given instant is especially shown in Fig. 2. Theviewing area or field 15 has a length equal to the radial depth of thespiral of apertures and a width equal to the pitch distance betweenadjoining apertures of a given channel andsuch that the number ofapertures exposed at any instant equals the number of channels inoperation. As hereinbefore mentioned I three channels have been shownfor illustrating the invention and the apertures 10, 2b, and 30 or anyother three adjacent apertures may at-any instant appear in and scan theviewing field. While these apertures are shown uniformly spaced theymight have any other suitable arrangement which permits only one.aperture representing a given channel being exposed at the same timeprovided the same arrangement of apertures or equivalent elements isprovided at the receiving station.

Fig. 3 is a side view of a portion of the scanning disc showing an endview of a prism such as is associated with each aperture of the disc.

The prism proper 33 is fastened to the scanning disc 31 by any suitablearrangement such as a clamping ring 34 in which the prism is fixed andwhich is bolted to the disc. The angles between front and rear faces ofthe various prisms are different, as is shown in Fig. 4.

Fig. 4 is a schematic drawing especially showing the direction of alight beam entering and leaving three adjoining scanning apertures andtheir associated refracting prisms, each directing a scanning light beambetween a different transmission channel and a different elemental areaof the field of View; Three views, A, B and C, in this figure aresections of the scanning disc along the lines A- A', 13-3, and C-C ofFig. 2. The relative positions of the three light sensitive cells 41a,42b, and 430 with respect to the scanning disc are shown in Fig. 4 andby means of dash-dot lines the path of the scanning beam from them toand beyond the prisms and apertures of the scanning disc'is also shown.In each case the scanning beam passes through the aperture in the discsubstantially parallel to its axis and upon passing out of theassociated prism the beam is deflected in the direction necessary toplace it in its proper transmission channel. The

prism associated with aperture 1a deflects the light to the position ofthe light sensitive cell 41a. The prism associated with aperture2bdefiects the light to the position of the light sensitive cell 421)and the prism associated with aperture 30 to the position of the lightsensitive cell,

430. This arrangement represents the direction of scanning light beamssimultaneously acting in a three channel system. As the scanning discrotates the apertures 4a, 5b, and ficcross the viewing field. and thelight passing through these .sirable to have a lens system 12-13, asshown in Fig. .1, back of the prisms in order that the light beams inaddition to being diverted into the respective channels by the prisms onthe disc are also directed as the prisms move across the scanning fieldtowards the center of the respective light sensitive cells.

In the foregoing, Fig. 4 has beendescribed with reference to thescanning operation at the transmitter. It is obvious, however, that asimilar optical arrangement including prisms associated with'theapertures of the scanning disc may be used at the receiving station, asshown in Fig. 1, in which case variable light sources are positionedback of the scanning disc in relatively the same position as the lightsensitive cells are in the'transmitting apparatus.

Fig. 5 shows a section of the scanning disc 31 and a light reflectingprism rather than a refracting prism. Either reflection or refractionmay be used by positioning the light sensitive cells or the lightsources accordingly. It is also obvious that other light deflectingdevices such as mirrors or the like may be associated with each of theapertures on the scanning disc.

Fig. 6 isa schematic representation of a multiple channel televisionsystem using the transmitting apparatusshown in Fig. 1 and receivingapparatus which produces the image on a large multiple element grid typereceiving lamp. Reference characters similar to those applied to thetransmitting apparatus shown in Fig. 1' have been applied to similarapparatus in Fig. 6 and the description heretofore made of Fig. 1 alsoapplies to the transmitting apparatus shown here. Thephotoelectric'currents generated by the transmitter are sent to thereceiver over any suitable transmission channels. The incomingphotoelectric or signal current received over each of the severalchannels is impressed upon separate receiving amplifier and controlnetworks for each channel. In the arrangement shown the transmittedcurrent is an alternating current of varying amplitude representative oflight variations above and below the average tone value of the objectbeing scanned. The receiving apparatus is similar to that shown in thepatent to Herbert E. Ives, No. 1,796,931, dated March 17, 1931. Theincoming alternating signal current received from each transmissionchannel is impressed upon its respective amplifier and control circuit110, 120, and 130 and is caused to modulate-a high frequency oscillatingcurrent generated by the oscillator 100. The modulated high frequencycurrent controlled by each channel is next passed through commutatordistributors 150, 160, and 170 for each of the respective. channels andfrom these distributorsto the multipleelectro'de glow dischargereceiving lamp 200. vThe receiving amplifier and control network 110,120, and 130 and the several commutator distributors are similar tothose shown for a single channelsystem in thepatent to FrankGray, No.1,759,504, dated May. 20, 1930'. The viewing field at the receivingstation is illuminated. by a large grid-type multiple electrode. glowdischarge lamp, one electrode being employed for each elemental area ofthe field. The commutator distributors contain one contact for eachelement or individual electrode of the glow discharge lamp andconnection is made between them by individual wires. Each commutatordistributor at any instant connects with only one electrode on the glowdischarge lamp 1 and thereby limits the illumination of the elementalarea defined by the connected electrode.

In this system the several channels .aresimulta neously operated and acorresponding number of elemental areas of the receiving lamp aresimultaneously illuminated. Each commutator 1 distribut'or has arotating brush and the brushes of all distributors are mounted upon asingle shaft which is driven in synchronism and in phase with thescanning apparatus by means of the driving motor 103.

'The' electrical circuits for the pictureproducing current flowingthrough the glow discharge lamp is between an individual electrode onthe lamp, each of which is connected with an individual contact in thecommutator distributor to the common'electrode of the lamp. The multipleelectrode glow discharge lamp is divided in accordance with the severalchannels bygrouping' the sections of each channel with its respectivecommutator distributor and connecting the common electrode of thedifierent sections to a common electrode connected with the properchannel. The common conductors 112, 122, and 132-may group thevarioustube sections according to channels and in turn connect with thereceiving circuit networks 110, 120, and 130, respectively'of thevarious channels. The arrangement of the connections between thecommutator distributors and the sections of the glow discharge lamp andof the common electrode of each. section of the glow discharge lamp soas to uniformly distribute the sections associated with each channel,preferably juxtapositioning the sections of the lamp representing"different channels, provides for connecting every third tube section,since three channels are shown, to their same respective channels.

The current for the modulated high frequency picture current may betraced for one channel from the receiving circuit network 110, conductor111, slip ring 153, brush arm 152, distributor brush 151, one of thecontacts in the commutator distributor 150, one of the individual leadwires from such contact to an individual connection through the multiplecontact panel 190 to an individual electrode on the glow discharge lamp200 and common return lead 112, back to the receiving circuit network110. A similar circuit may be traced in connection with each of theother channels. As many individual wires connect between the commutatordistributors contacts and the glow discharge lamp as there areindividual electrodes on the lamp, though in the drawing this pluralityof wires is shown by a few single lines for simplicity.

The glow discharge lamp in the arrangement shown is operatedby amodulated high frequency terminal of this oscillator connects by meansof the conductor 102 to-the auxiliary electrode 205 on each tube sectionof the glow discharge lamp 200, while the other terminalof theoscillator connects through the receiving circuit networks of theseveral channels with the common electrodes in the glow discharge lampthrough the several lamps common return conductors 112, 122, and 132.The responseof a glow discharge lamp is much more. sensitive to startingand to small current variations if the lamp is already under excitationwhen the signal current is impressed thereon and this fact is takenadvantage of by continuously exciting the lamp through a special set ofelectrodes so arranged as to avoid interfering with the luminosity ofthe viewing screen. A large panel of ground glass 220 p0 sitionedclosely in front of the glow discharge lamp 200 may be added to form apicture receiving or viewing surface. This may, however, be omitted whenthe audience is a considerable distance from the glow discharge lamp.

A multiple channel system of three channels has been shown anddescribed, but this number, as heretofore stated, may be increased ordecreased. The operation of each channel is substantially the same asanyother channel and the apparatus used in each channel may be in mostrespects substantially the same as that disclosed in the patent to FrankGray, No. 1,759,504, dated May 20,1930, supra. Further details of thisreceiving apparatus, particularly the glow discharge lamp 200, may befound in the patent to .H. E. Ives, No. 1,796,931, dated March 17, 1931,supra.

A further embodiment of this invention comprising light amplificationprovides for making aphotographic filmrecord of the object, developingand fixing the film, and then passing the developed film through beamsof light directed upon light sensitive cells thereby causing the lightsensitive cells to generate electric currents varying in accordance withthe light tone values of elemental areas of the film. Several elementalareas are simultaneously scanned, the number equaling thenumber ofchannels simultaneously in operation for transmission.

A general view of the transmitting apparatus comprising a moving picturerecording camera, film, photographic developing and fixing apparatus,moving picture projecting apparatus for projecting the picture recordinto television transmitting scanning apparatus for converting therecord into varying electric currents for transmission, andsynchronizing apparatus, is shown in Fig. 7. The various componentelements of thetransmitting apparatus are mounted within and upon theframework 300. The moving picture camera 301 may be any suitablestandard moving picture camera. It is so associated with the othertransmitting apparatus that the moving picture film 302 after beingexposed for the picture record passes through the photographicdeveloping and fixing apparatus 320. Any suitable developing and fixingprocess may be used, though in the drawings only two steps are indicatedby tanks 321 and 322 for the developing and fixing operations,respectively. Such other steps as .sion channel. After through thetransmitting apparatus, it may be impresses the light from eachelemental area simultaneously being scanned onto the light sensitivecells 341a, 342b, and 3430, one for each channel; The light sensitivecells connect through suitable amplifying networks to individualtransmission channels as heretofore explained. Synchronizing apparatusis arranged to transmit synchronizing current over a suitabletransmisthe film has been passed wound upon a reel 360or otherwisedisposed of.

The transmitting apparatus is positioned so that the moving picturecamera 301 is directed upon the object or field whose image is to betransmitted. .Unexposed moving picture film 302 is placed in themagazine 304 of the moving picture camera 301 and then threaded throughthe various apparatus units, as shown in the drawings and finally to thestoring 'reel 360. Suitable guides and driving gearing control themovement of the film at various positions. The film in passing throughthe moving picture camera 301 and the picture projecting apparatus 350is intermittently driven. The movement of the film at the differentpoints is maintained in proper synchronism with the different apparatuselements by means of gearing, not shown in the drawing, interconnectingthe various driving gears, and all connected with the synchronousdriving motor 332 which is of usual construction but preferably of goodsize to overcome any tendency to change of speed with changing reactionsfrom the apparatus driven thereby. Connection of this gearing with themotor may be made through any suitable arrangement such as the worm andgear connection 334 and 335. The movement of the film through the camera301 is obtained by any well known standard gearing arrangement '303associated with the camera; In the projecting apparatus 330 the film isfed in and out at a uniform rate by means of the sprocket gearing 351and 352, While it is driven intermittently by the sprocket gearing 354and 355, all of which are connected by well known means to the drivinggearing from the motor element 322. The sprocket gearing 351 also movesthe film through the developing and fixing tank 321 and 322,respectively.

The exposed film after being developed and fixed is passed through theprojector 350, where it passes through an intense beam of light from theprojector lamp 355 and a lens system 357 and 358, which projects inaccordance with standard practice an image of the picture upon thescanning disc 331 of the television scanning apparatus 330. The scanningapparatus is the same as shown in Fig. 1, with the exception that asection of the scanning disc is blank during the movement of the filmfrom one frame to the next, and the description heretofore given isotherwise applicable here. During this film shift photoelectrictransmission ceases and the transmission channels are accordingly lesseffectively used than would be the case with continuous scanning assubsequently described in a modified arrangement. A plurality ofelemental areas, one for each channel, of the image projected from thephotographic film record upon the scanning disc, are simultaneouslyscanned and photoelectric currents'for the different elemental areas aregenerated in each of the different light sensitive cells originatingdifferent electrical transmission channels. 1

A general view of the receiving apparatus comprising televisionreceiving scanning apparatus, a moving picture recording camera, filmphoto-' graphic developing and fixing apparatus, mov-' ing pictureprojecting apparatus, and synchronizing apparatus, is shown in Fig. 8.The various component elements of the receiving apparatus, many of whichare similar to corresponding elements in the transmitting apparatus, aremounted within and upon the framework .400. The moving picture camera401 may be any suitable standard moving picture camera. This receivingcamera is positioned in front of the television receiving apparatus 430in such relation thereto that the image produced by the television.apparatus is focused upon the moving picture film 402. The televisionapparatus contains a plurality of light sources 481a, 482b, and 4830,each terminating a separate incoming electrical transmission channel.The light intensity of these various lamps varies in accordance with theincoming image signals. The arrangement of the television receivingapparatus here is similar, with the exceptionthat a section of thescanning disc is blank during themovement of the .film from one frame tothe next,to that shown in Fig. 1. The scanning disc 431 is similar tothe scanning disc in the transmitting apparatus and it is operated by asynchronous driving motor element 432, which may be of any well knownform and preferably of good size, in synchronism and in phase with thetransmitting apparatus. The transmitting scanning disc scans thephotographic image of thepicture to be transmitted in a series ofparallel lines, groups of juxtapositioned lines representing thedifferent channels, thereby setting up varying picture currents whosestrength at any instant corresponds with the light intensities of thevarious elemental areas of the image on the transmitting film. Thesecurrents cause corresponding variations in the light intensity of theseveral light sources 481a, 482D and 4830, which in turn are caused tosuccessively illuminate the corresponding elemental areas of the;receiving film at each instant with a light intensity similar to that ofthe image on the film at the transmitting station. A positive picture isthus recorded on the receiving film 402 which corresponds tothe negativepicture on the transmittingfilm 302., The moving picture recordingfilm402 after being exposed for the picture record passes through thephotographic developing and fixing apparatus 420 containing the twotanks 421 and 422, respectively. However, as explained in connectionwith the transmitting apparatus any suitable process may be used andsuch steps as washing and drying the film may be incorporated. The filmafter being fixed is passed without drying through picture projectingapparatus 450. An image of the picture is projected in accordance withstandard moving picture practice upon a suitable screen for viewing.After the film has passed through the projecting apparatus it may bewound upon a reel 460 or otherwise disposed of. The receiving apparatusis positioned so that the moving picture projecting apparatus projectsthe picture on a large screen 499 in front of the audience.

Unexposed moving picture film 402 is placed in! the magazine 404 of themoving picture camera 401 and then threaded throughthe variousapparatusunits, as shown in the drawings and finally to the storing reel 460,substantiallythe same as in the transmitting apparatus. and drivinggearing control the movement of the film at the various positions. Thefilm-in passing through the moving picture camera 401 and the movingpicture projecting apparatus 450 is intermittently driven, while themovement of the film at the dilferent points ismaintainedin propersynchronism with the diiferent' apparatus Suitable guides.

elements by means of gearing, not shown in the drawings, interconnectingthe various driving gears and all connected with the synchronizingdriving motor 432. Connection of this gearing with the motor may be madethrough the worm and gearing connections 434 and. 435. The movement ofthe film through the camera 401' is obtained by any well known standardgearing arrangement 403 associated with the camera.

In the projecting apparatus 450 the film is fed in and out atna uniformrate 'by means of a sprocket gearing 451 and 452 'while it is drivenintermittently by'the sprocket gearing 454 and 455, all of which areconnected by well known means to the driving gearing. ofthe motorelement 432. The sprocket gearing 451 also moves the film through: thedeveloping and fixing tanks 421 and 422.

The exposed film after being developed and fixed is passed to thepicture projector 450, where it is passed through an intense beam oflight from the projector lamp 456 and a lens system 457 and 458, whichprojects in accordance with standard practice an image of the pictureupon a large viewing screen 499.

' In the foregoing description relating to Figs 7 and 8 the movement ofthefilm through most the moving pictures in accordance 'with'standard.

practice and moved continuously in the projecting apparatus 350 fromwhich an image of the picture is projected into the television scanningand transmitting apparatus '330 where it i's-trans lated intophotoelectric current. With the film moving continuously at, the proper,rate before the television scanning apparatus, the scanning aperturesand associated prisms 'of the scanning disc may be positioned in acircle on the scanning disc, as shown in Fig. 9, and the continuousmove-v ment at the proper rate of the film normal to the movement of thescanning apertures causes each aperture to scan a different line acrossthe film, thus producing the same result as having the film move theproper amount intermittently in front of a scanning disc having itsapertures spirally arranged. In this arrangement the viewing field has alength substantially equal to the product of the Width of a scanningline and the number of apertures in the scanning disc, and

governed by the movement of the sensitized film or plate. Fig. 9 shows ascanning disc 31' having apertures la, 21), 3c, 4a',.5b', and 6c,etc.,.circularly arranged. Any adjacent three apertures, such' as .112,2b, and 30' each of different chanfiels may at any instant appear in andmove across the scanning zone or belt as shown by the opening in theplate in front of the scanning disc. Thetposition of the moving film isshownby the dot-dash lines F. Successive lines of elemental areas acrossthe picture are transmitted irrespective of whether the system'is asingle or a multiple channel system. The positioning of the apertures incircular arrangement and continuai'ly moving an associated film is oldin a singlechan'nel but dividing the scanning into a plurality. ofchannels for multiple channel operation as heredisclosed is novel; Asimilar modificatiorr may be: made in the television receiving element.430 and the film in the receiving camera 401 moved at'a jun'iforr'nrate. In projecting the finished film onthescreen for viewing anystandardpicture projector 450, may be used. Moving the film at a uniformrate for electrO optical transmission has the decided advantage of.permitting the television transmitting and receiving apparatus tooperate continuously and not cease photoelectric transmitting andreceiving operationsbetween pictures as is required when the film isintermittently advanced in the usual way from picture to picture. Thisadvantage is important in effecting economies and efficiencies in theuse of the transmission system and apparatus. The loss in time due tointermittently advancing the film may befifteen to twenty per cent ofthe total time which-is the equivalent of one channel in a five or sixchannel system.

It is also obviousthat different types of transmitting apparatuscan beused with a given type of receiving apparatus or vice versa. Forexample, the transmitting apparatus employing light amplification bymeans of a film as shown in Fig. 7 might be used with the grid type glowdischarge lamp receiver shown in Fig. 6 or the transmitting apparatusshown in Fig. 1 might be used with the light amplification arrangementemploying a film as shown in Fig. 8. However, when onlyonephotographic'process is employed since .the photographic processreproduces in general in a reciprocal manner, means must be provided forso warping the characteristics of the picture transmission that thenon-linear characteristic inherent in the photographic process whencarried'through only one of the two operations is -compensated for.Either optical or electrical distortion may be employed for efiectingthis compensation. Also the proper electrical polarity must be made inthe circuit connection in order that received photoelectric current mayproduce a positive pictureatthe receiver irrespece tive of thecombination of apparatus units used. Other. combinations of.transmitting and receiv-' ing apparatus are obvious) What is claimediSi... 3

1; In a multiple channel electro opti'calsys tem, a rotatable scanningdisc comprising a plu rality of light beam directing. optical prismsarranged in a single line upon said disc within 360. and means forcausing light beams to pass simultaneously from a number of .said prismsequal in number to the transmission channels and to cross a viewingfield in juxtapositioned scanning lines; l

2. In. a multiple channel electric-optical system, a rotatable.disccoinprising a plurality of. lightdirecting optical prisms spirallyarranged upon said disc in a single spiral, and means for causing lightto pass simultaneously through a number of said prisms equal in numberto the transmission channel's.

3'. In a multiple channel electro-optical system, a rotatable disccomprising a plurality of apertures in a single row within 360, andmeans for causing light to pass simultaneously through a number of saidapertures equal 'to the number of transmission channels.v

4. The method. of m'ulti-channel television which comprises scanning aseries or" parallel strips of a field of .view in succession for eachchannel, each strip comprising a. series of elemental areas, the stripsfor each channel being interspersed with strips for the'other channel"or channels, the scannings for allfichannels being concurrent and thetime of beginiiingof scanning of each strip being different from thatfor an adjacent-strip by the same amount.

5. A multi-channel television system comprising means for scanninga'series of fparallel str ips of a field of view in successionand in theorder of their occurrence across the field, each strip comprising aseries of elemental areas, the time of beginning of scanning of reachstrip being fi'different from that for. an-adiacent strip by :the sameamount, and which is less than a line s'canni'ng period, and me'ansforcausing different portions of the field to be transmitted over'different channels concurrently.

6. A multi-channel television system comprising means-f or scanningparallel strips of: elemental areas of a field of view and for causingthe period ofscanning of each strip to substantially overlap that ofeach strip adjacentthereto-and means for causing diirerent portions ofthe field to be transmitted o'ver difierent channels 'concurrently.

i HERBERT E.

